Preparation of metal mesoporphyrin compounds

ABSTRACT

A method of preparing metal mesoporphyrin halide compounds is described. The metal mesoporphyrin halide compound may be formed by forming a novel mesoporphyrin IX intermediate compound and then converting the mesoporphyrin IX intermediate to the metal mesoporphyrin halide through metal insertion. The novel intermediate compound may be formed by a catalytic hydrogenation of hemin in acid and subsequent recovery.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of co-pending U.S. patentapplication Ser. No. 10/812,156 filed Mar. 29, 2004, which is acontinuation-in-part of U.S. application Ser. No. 10/453,815, filed onJun. 3, 2003, now U.S. Pat. No. 6,818,763, which claims the benefit ofU.S. Provisional Application No. 60/385,498, filed on Jun. 4, 2002, thedisclosures of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention generally relates to metal mesoporphyrin halidecompounds and processes for their preparation. More specifically, itrelates to processes for making novel intermediate compounds, which canbe converted to such mesoporphyrin halide compounds.

Tin (IV) mesoporphyrin IX dichloride or stannsoporfin is a chemicalcompound having the structure indicated in FIG. 1. It has been proposedfor use, for example, as medicament in the treatment of various diseasesincluding, for example, psoriasis (U.S. Pat. No. 4,782,049 to Kappas etal.) and infant jaundice (for example, in U.S. Pat. Nos. 4,684,637,4,657,902 and 4,692,440). Stannsoporfin is also known to inhibit hememetabolism in mammals, to control the rate of tryptophan metabolism inmammals, and to increase the rate at which heme is excreted by mammals(U.S. Pat. Nos. 4,657,902 and 4,692,400 both to Kappas et al.).

Processes for obtaining stannsoporfin are known in the art.Protoporphyrin IX iron (III) chloride or hemin, of the structuralformula indicated in FIG. 2, is commonly used as starting material. Thehemin is generally hydrogenated to form an intermediate mesoporphyrin IXdihydrochloride, which is subsequently subjected to tin insertion,yielding stannsoporfin.

One prior method for the preparation of the intermediate mesoporphyrinIX dihydrochloride has involved catalytic hydrogenation of hemin overPd(0) in formic acid at elevated temperature. Column chromatography ofthe resulting intermediate obtained by such a method yields anintermediate mesoporphyrin IX dihydrochloride product that reportedlycontains about 15% of an unidentified impurity. Another preparationmethod for this intermediate has been typically performed at lowertemperatures with heating hemin in formic acid in the presence ofpalladium catalyst. This process is reported to reduce the amount of theunidentified impurity; however, the reaction is difficult to drive tocompletion without decomposition of the intermediate product.

The above referenced methods for the preparation of the mesoporphyrin IXintermediate are used to produce only small, gram scale quantities ofthe product, and the product further requires subsequent isolation andpurification, generally by preparative or column chromatography.Additionally, those methods in which hydrogenation is carried out atlower temperatures yield incomplete reactions, and when highertemperatures are used, degradation of the intermediate product isobserved. Consequently, the crude intermediate product requirespurification. Furthermore, the above referenced procedures requireexceedingly high solvent volumes, thus making the process unsuitable forindustrial scale up, since isolation of mesoporphyrin IX dihydrochlorideor its free base is performed using a filtration process. Suchfiltrations and subsequent washings of the products are time-consuming,making the large-scale isolations costly and difficult. Additionally,the limited stability of mesoporphyrin IX in hydrochloric acid at theelevated temperatures required to form the dihydrochloride alsocomplicates the industrial scale up of this process.

The insertion of various metals into porphyrin rings has been describedby Fischer and Neumann (Ann. Chem. (1932), 494, 225). The reaction forthe insertion of tin is performed in an acid, typically acetic acid, andfurther typically under reflux, using Sn (II) in the presence of anoxidant. A modified process is also described by Fuhrhop and Smith, asreported in “Porphyrins and Metalloporphyrins” p. 757, Elsevier,Amsterdam, 1975, to include sodium acetate, which buffers the solutionand enhances deprotonation of the porphyrin. In most cases, the metalmesoporphyrin halide product crystallizes directly from the reactionmixture on cooling. Such crystallization may be enhanced by the additionof water or methanol.

SUMMARY OF THE INVENTION

One or more embodiments of the present invention provides a novelprocess for the preparation of metal mesoporphyrin halides thatovercomes some of the difficulties of the processes known in the art.

It has now been discovered that, if the catalytic hydrogenation of heminis conducted in formic acid, in two distinct states, each usingdifferent reaction conditions, a novel intermediate compound, amesoporphyrin IX formate, is formed. This compound can be precipitatedso that it can be isolated in a substantially pure, solid form. Then thesubstantially pure formate intermediate can be reacted to form a metalmesoporphyrin halide. This reaction of the formate intermediate can beaccomplished in a single reaction with a metal to form a metalmesoporphyrin halide. Alternatively, the mesoporphyrin formate can bepurified, and the purified intermediate can be used to form a metalmesoporphyrin halide. In another embodiment, the purified or unpurifiedmesoporphyrin formate can be converted to a mesoporphyrin IXdihydrochloride and reacted with insert metals such as tin, and obtainmetal mesoporphyrin halides with a high degree of purity, capable offurther purification if necessary, by simple procedures capable of beingconducted on an industrial scale. Preferably, the intermediate formateis purified, converted to a mesoporphyrin dihydrochloride, and themesoporphyrin dihydrochloride is reacted to form a metal mesoporphyrinhalide.

Thus the invention provides, from one aspect, a process of preparing amesoporphyrin IX formate, which comprises subjecting hemin to catalytichydrogenation in formic acid, said hydrogenation being conducted in twosuccessive steps comprising a first step of subjecting a mixture ofhemin and a hydrogenation catalyst in formic acid to a first temperatureand pressure for a first period of time. In one embodiment, the hydrogenpressure may be between about 30-60 psi and the temperature may bebetween about 85-95° C. The temperature may be held within that rangefor a period of about 1-3 hours.

A second step includes subjecting the mixture to a second temperatureand pressure for a second period of time. In one embodiment, the secondhydrogen pressure can be between about 30-60 psi and the temperaturesmay be between about 45-50° C. The mixture may be held to thistemperature for a period of between about 3-6 hours. Mesoporphyrin IXformate is then recovered from the reaction mixture by precipitationwith an organic solvent, for example an ether. Mesoporphyrin IX formate,which has the structural chemical formula indicated in FIG. 3, is anovel chemical compound.

Alternatively and preferably, the reactor may be pressurized withhydrogen gas prior to the heating step. Pressurizing the reactor withhydrogen prior to heating, in the first step of the process, reducesdegradation, while exceeding the times and the temperatures set outabove for the first step increases degradation. On the other hand,shorter reaction times and lower temperatures will lead to undesirabledecreases in conversion, leading to low product yields. The second stepas defined above completes the conversion of the hemin (ProtoporphyrinIX iron (III) chloride) to mesoporphyrin IX formate.

Isolation of the intermediate product as a formate provides a readilyfilterable intermediate, filtering and washing of which to obtain atleast a substantially high purity intermediate product (about >97%) is asimple procedure. The purity of the intermediate is important in themanufacturing of the final product, whether stannsoporfin or other metalmesoporphyrin halides, in that a higher purity intermediate produces ahigher purity product. According to one or more embodiments, themesoporphyrin IX formate intermediate can then be subjected to furtherpurification such as reaction with metal scavengers and then convertedto metal mesoporphyrin IX dihydrochloride.

Another aspect of the present invention comprises a process ofconverting a mesoporphyrin IX dihydrochloride to a metal mesoporphyrinhalide which comprises subjecting the mesoporphyrin IX dihydrochlorideto a chemical metal insertion process by reaction with a metal halidecompound, under buffered, acidic reaction conditions and in the presenceof an oxidant; and recovering the metal mesoporphyrin halide from thereaction mixture.

The invention provides, in another aspect, a process of purification ofa metal mesoporphyrin halide, which comprises the steps of dissolvingthe metal mesoporphyrin halide in an aqueous basic solution to obtain adissolved metal mesoporphyrin halide; treating said dissolved metalmesoporphyrin halide with charcoal to obtain a treated metalmesoporphyrin halide; adding said treated metal mesoporphyrin halide toa first aqueous acid solution to obtain a precipitated metalmesoporphyrin halide; triturating said precipitated metal mesoporphyrinhalide in a second aqueous acid solution at elevated temperature toobtain a pharmaceutical grade pure (about or more than 97%) metalmesoporphyrin halide; and drying the pharmaceutical grade pure metalmesoporphyrin halide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the chemical structure of tin mesoporphyrin chloride(tin (IV) mesoporphyrin IX dichloride) or stannsoporfin.

FIG. 2 illustrates the chemical structure of protoporphyrin IX iron(III) chloride or hemin,

FIG. 3 illustrates the chemical structure of mesoporphyrin IX formate;

FIG. 4 illustrates the conversion of protoporphyrin IX iron (III)chloride (ferriporphyrin chloride or hemin) to mesoporphyrin IX formateto mesoporphyrin IX dihydrochloride, in accordance with one embodimentinvention; and

FIG. 5 illustrates the conversion of mesoporphyrin IX dihydrochloride toa tin mesoporphyrin chloride (tin (IV) mesoporphyrin IX dichloride) orstannsoporfin, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

According to one embodiment of the invention, illustrated inaccompanying FIG. 4, hemin is hydrogenated in formic acid, over anappropriate metal catalyst such as, for example, palladium, platinum ornickel, among others, under a hydrogen atmosphere, at elevatedtemperatures. Preferred embodiments of the invention involve the use ofpalladium on carbon as metal catalyst. According to one or moreembodiments, in the first stage of hydrogenation, the temperature ofhydrogenation is held at about 85-95° C. for a period of about 1-3hours. Most preferred conditions are a temperature of about 90° C. and atime of about 1 hour.

In one or more in embodiments, in the second stage of hydrogenation, thereaction mixture is cooled to about 45-50° C. and hydrogenated for afurther period of time of about 3-6 hours, in order to convertsubstantially all hemin (protoporphyrin IX iron (III) chloride) tomesoporphyrin IX formate. This second stage is also conducted in formicacid. The same catalyst may be used as above, so that the two stages ofthe process may be conducted in the same reactor. Optionally, a furthercharge of hydrogen may be supplied to the reactor prior to commencingthe second stage. The second hydrogenation stage increases the yield ofthe mesoporphyrin IX formate, while reducing the amount of impurities inthe final metal mesoporphyrin halide.

In contrast to previously described methods, the mesoporphyrin IXintermediate compound in the present invention is not isolated as adihydrochloride, but rather as a formate salt.

The mesoporphyrin IX formate may be isolated from the formic acidsolution by the addition of a solvent such as an ether or other organicsolvent, leading directly to the mesoporphyrin IX formate intermediate,which is further subjected to drying. Ethers such as, for example,methyl tert-butyl ether, diethyl ether or di-isopropyl ether, amongothers, may be used. Preferred embodiments of the invention involvemethyl tert-butyl ether.

The amounts of solvent used in the process according to the inventionare much lower than those used in the referenced processes that involvethe formation of a dihydrochloride intermediate; such smaller volumesallow for less filter time. Ratios of amount of hemin to amount ofsolvent of about 1:10 to about 1:20 may be used. In addition, thefiltration and washings of the mesoporphyrin IX formate are rapid. Afterdrying, the crude intermediate formate is obtained, in high yields(about 80-95%) and its purity, established by HPLC, is about or above97%. The intermediate formate obtained in accordance with the process ofthe invention is of quality equal to or better than that of theintermediate mesoporphyrin IX dihydrochloride produced in the processdescribed in the prior art, after purification by preparativechromatography.

According to one or more embodiments of the present invention, themesoporphyrin IX formate obtained above and shown in FIG. 4 can befurther purified by dissolving the formate in formic acid. A metalscavenger may be utilized to purify the formate to remove residual metalcatalysts. After the scavenger is removed, the mesoporphyrin IX formatesolution is mixed with hydrochloric acid to convert the formate tomesoporphyrin IX dihydrochloride. Preferred metal scavengers include,but are not limited to, silica bound scavengers such as Si-thiol,Si-thiourea, Si-triamine, and Si-triaminetetraacetatic acid, which areavailable from Silicyle® Incorporated. The purification process iscarried out for a time sufficient to remove residual metal catalyst suchas palladium, which would otherwise remain as an impurity. Preferably,the purification process proceeds for more than 10 hours and less than20 hours, for example, about 16 hours. It will be understood that theinvention is not limited to any particular time, and that longer timesmay result in a higher purity product. The metal scavenger is thenremoved by charging a filtering aid such as celite and additional formicacid into the mixture. Then, the mixture is filtered to providefiltrate, which is vacuum distilled and cooled to concentrate thefiltrate. The concentrated filtrate is then added to 1 N hydrochloricacid, and the resultant suspension is isolated by filtration to formmesoporphyrin IX dihydrochloride. Applicants have discovered that theseadditional processing steps to scavenge metal from the mesoporphyrin IXformate intermediate and form a mesoporphyrin IX dihydrochlorideintermediate yields a higher purity end product (tin mesoporphyrin IXdichloride).

The insertion of metal into mesoporphyrin IX dihydrochloride to obtainmetal mesoporphyrin halide is described below with specific reference totin, to prepare stannsoporfin, a known pharmaceutical and a specificpreferred embodiment of the invention. It is not intended that the scopeof the invention should be limited thereto, but is generally applicableto preparation of mesoporphyrin halides, for example, but not limitedto, mesoporphyrin chlorides, of other metals such as, for example, iron,zinc, chromium, manganese, copper, nickel, magnesium, cobalt, platinum,gold, silver, arsenic, antimony, cadmium, gallium, germanium andpalladium, among others.

Preparation of mesoporphyrin halides of these other metals simplyentails a substitution of a halide such as chloride, bromide or iodideof the chosen metal in place of stannous chloride in the processdescribed, in substantially equivalent amounts.

The second stage of the process according to one or more embodiments ofthe invention is illustrated in FIG. 5. Mesoporphyrin IX dihydrochlorideis subjected to heating with a tin (II) carrier in acetic acid, in thepresence of an oxidant, at reflux. Preferably, the heating is performedwith aeration, for example, by an inflow of 6% oxygen mixed withnitrogen for about 24-48 hours. Air inflow could also be used to aerateduring heating. Tin (II) carriers such as tin (II) halides or tin (II)acetate can be used. The reaction may also be carried out in thepresence of suitable acetate counter ions include ammonium, sodium orpotassium ions. Oxidants such as oxygen from air or in pure form as wellas hydrogen peroxide can also be used. In one exemplary embodiment ofthis second stage, mesoporphyrin IX formate is subjected to heating withtin (II) chloride in acetic acid, buffered with ammonium acetate, andthe reaction is conducted with aeration, at reflux. The ammonium acetatecan be eliminated. Tin mesoporphyrin chloride is isolated from thereaction mixture by the addition of water, followed by filtration. Priorto drying at about 90-100° C., the cake is triturated into hot, dilutehydrochloric acid, preferably of concentration of about 0.1N-6N, at anelevated temperature, of about 90-100° C. The crude, substantially puretin mesoporphyrin chloride (crude tin (IV) mesoporphyrin IX dichloride)is obtained with a yield of about 75-95% and a purity of about 95%, asjudged by HPLC analysis.

The tin mesoporphyrin chloride so obtained may be further purified bydissolving the product in an aqueous inorganic base solution, preferablydilute ammonium hydroxide, followed by treatment with charcoal. Theproduct is then re-precipitated by addition to an acid solution, such asacetic acid, hydrochloric acid or a mixture thereof. The abovedissolving charcoal treatment and re-precipitation steps may be repeateda number of times, typically about 1-3 times in order to ensure thedesired purity. Prior to drying, the cake is triturated in hot, dilutehydrochloric acid of a concentration of about 0.1N-6N, at an elevatedtemperature of about 90-100° C., in order to remove any residualammonium salts. The tin mesoporphyrin chloride product (tin IV)mesoporphyrin IX dichloride or stannsoporfin) is obtained in a yield ofabout 50-70%, with an HPLC purity of about or greater than 97%.

The invention may also be performed to produce substantially pure orpharmaceutical quality tin mesoporphyrin chloride (tin (IV)mesoporphyrin IX dichloride or stannsoporfin) in large scale quantities,such as quantities exceeding about 0.1 kg through and including multiplekilogram amounts, by slight modifications of the above procedure, suchas increased reaction or drying times as appropriate based upon theincrease in scale of the starting reactants. Temperature and pressuretimes likewise can be modified as needed within the scope of thisinvention. The tin mesoporphyrin chloride product (tin (IV)mesoporphyrin IX dichloride or stannsoporfin) is obtained in thelarge-scale production process in a yield of about 60-90%, with an HPLCpurity of about 97%.

The invention will be further described, for illustrative purposes, withreference to the following specific experimental examples.

EXAMPLE 1 Preparation of Mesoporphyrin IX Formate

A 2000 ml hydrogenation vessel was charged with 40.0 g hemin, 4.0 g 5%Pd/C (50% water by weight), and 800 ml 96% formic acid. Since hemin andmesoporphyrin IX formate as well as all reaction intermediates arereportedly light sensitive materials, care was taken throughout thisentire procedure to minimize the exposure of the reaction to visible orultraviolet light.

The vessel was flushed with a nitrogen flow for 10 minutes. Withvigorous stirring, it was then pressurized to 50 psi with hydrogen forten minutes; then depressurized, and the cycle repeated. The vessel wasfurther pressurized to 50 psi with hydrogen and the temperature wasraised to 90° C. over approximately 20 minutes.

The hydrogenation reaction was maintained at 90° C. and 45-55 psi for1-1.5 hours. The reaction mixture was not stable for extended periods oftime at 90° C. The time at this temperature was sufficient to dissolveall hemin and convert the majority of this material to the intermediateand final product, mesoporphyrin IX formate. The reaction was cooled to50° C./50 psi over 20 minutes. This pressure and temperature weremaintained for 3 hours. The reaction mixture was shown to be stable atthis temperature for up to 48 hours. The reaction was cooled to 20-25°C., de-pressurized, and flushed with nitrogen.

The catalyst was removed by filtration through a bed of 20 g celite. Thefilter cake was rinsed with 3×50 ml formic acid and the filtrate wascharged to a 2000 ml three-necked, round-bottom flask equipped with amagnetic stirbar, thermometer, and distillation bridge. The formic acidsolvent was distilled off under aspirator vacuum to a residual volume of200 ml. The distillation bridge was replaced with an addition funnel.With moderate agitation, 800 ml methyl tert-butyl ether was added dropwise over 30-60 minutes. The resultant suspension was agitated at 20-25°C. for 60 minutes prior to cooling to −20 to −25° C. for 1 to 2 hours.The suspension was filtered under reduced pressure. The filtercake wasrinsed with 100 ml filtrate, followed by 2×50 ml methyl tert-butyl etherand dried under high vacuum at 40-60° C. for 24 hours. About 30-38 g ofmesoporphyrin IX formate were obtained (yield of 75-95%).

EXAMPLE 2 Preparation of Substantially Pure Tin Mesoporphyrin Chloride(Tin (IV) Mesoporphyrin IX Dichloride or Stannsoporfin)

A dark 1000 ml three-necked, round-bottom flask equipped with amechanical stirrer, condenser, bubbler, and an aeration tube was chargedwith 30.0 g mesoporphyrin IX formate, 34.5 g tin (II) chloride, 7.1 gammonium acetate, and 600 ml acetic acid. The suspension was stirred at20-25° C. for 30 minutes. Mesoporphyrin IX formate and tin mesoporphyrinas well as all reaction intermediates are reportedly light sensitivematerials therefore care was taken throughout this entire procedure tominimize the exposure of the reaction to light.

The reaction was warmed to reflux, with aeration, for 3 to 4 hours. Thereaction was shown to be stable at 110-115° C. for up to 48 hours. Oncecomplete, the reaction mixture was cooled to 60-70° C. and 300 ml waterwas added while cooling to 20-25° C. over 60 minutes. The suspension wasfiltered under reduced pressure. The filtercake was rinsed with 2×60 mlwater. A dark, 1000 ml, three-neck, round-bottom, flask equipped with astir bar, thermometer, condenser, and nitrogen purge was charged withthe wetcake from the above step, and 500 ml 1N HCl. The resultantsuspension was warmed to 90° C. for 1 hour. The suspension was filteredunder reduced pressure. The filtercake was rinsed with 2×50 ml 0.1N HCland dried under high vacuum at 80-90° C. for 24 hours. About 25 to 28 gof crude, substantially pure (about or exceeding 95% purity) tinmesoporphyrin chloride (tin (IV) mesoporphyrin IX dichloride orstannsoporfin) was obtained for a yield of about 83-93%.

EXAMPLE 3 Further Purification of Crude, Substantially Pure Tin (IV)Mesoporphyrin Chloride (Tin (IV) Mesoporphyrin IX Dichloride orStannsoporfin)

A darkened, 250 ml, one-neck, round-bottom flask equipped with amagnetic stirbar and nitrogen purge was charged with: 10.0 g tin (IV)mesoporphyrin chloride (tin (IV) mesoporphyrin IX dichloride), 125 mlwater, and 4 ml 28% ammonium hydroxide, a sufficient amount of ammoniumhydroxide to adjust the pH to 9.0-10.0. The suspension was stirred at20- 25° C. for 20-30 minutes to effect dissolution. As tin (IV)mesoporphyrin is light sensitive, dark conditions were maintainedthroughout this reaction sequence.

The flask was charged with 0.5 g Darco KB, and a 1.5 g Celite. The darksuspension was stirred at 20-25° C. for 1 hour. The suspension wasfiltered under reduced pressure through a bed of celite using a 5.5 cmBuchner funnel. The flask and filtercake were rinsed with 2×10 ml water.A dark, 1L, one-neck, round-bottom flask equipped with a magneticstirbar, addition funnel and nitrogen purge was charged with 375 mlacetic acid, and 10 ml 37% hydrochloric acid. The filtrate from thecelite filtration step was charged to the addition funnel and addeddropwise to the stirring acid solution over 30-45 minutes. Thesuspension was stirred at 20-25° C. for 1-2 hours; then filtered underreduced pressure using a 7 cm Buchner funnel. The filtercake was rinsedwith 2×10 ml water.

A darkened, 250 ml, one-neck, round-bottom flask equipped with amagnetic stirbar and nitrogen purge was charged with the tinmesoporphyrin wet cake from the above step, 125 ml water and 4 ml 28%ammonium hydroxide. The suspension was stirred at 20-25° C. for 20-30minutes to effect dissolution and the pH adjusted to about 9.0-10.0 withadditional ammonium hydroxide. The flask was charged with 0.5 g DarcoKB, and 1.5 g Celite. The dark suspension was stirred at 20-25° for 1hour. The suspension was filtered under reduced pressure through a bedof celite using a 5.5 cm Buchner funnel. The flask and filtercake wererinsed with 2×10 ml water.

A dark L one-neck, round-bottom flask equipped with a magnetic stirbar,addition funnel and nitrogen purge was charged with 375 ml acetic acid,and 10 ml 37% hydrochloric acid. Once the addition was complete, the pHwas adjusted to about less than or equal to 1 by the addition of 37%hydrochloric acid. The filtrate from the above celite filtration stepwas charged to the addition funnel and added dropwise to the stirringacid solution over 30-45 minutes. Once the addition was complete, the pHwas adjusted to about less than or equal to 1 by the addition ofhydrochloric acid. The suspension was stirred at 20-25° C. for 1-2hours; then filtered under reduced pressure using a 7 cm Buchner funnel.The filtercake was rinsed with 2×10 ml water.

A darkened, 250 ml, one-neck, round-bottom flask equipped with amagnetic stirbar and nitrogen purge was charged with tin mesoporphyrinwet cake from the above step, 125 ml water, and 4 ml 27% ammoniumhydroxide. The suspension was stirred at 20-25° C. for 20-30 minutes toeffect dissolution. The pH was adjusted to about 9.0-10.0 withadditional ammonium hydroxide. The flask was charged with 0.5 g DarcoKB, and 1.5 g Celite. The dark suspension was stirred at 20-25° C. for 1hour. The suspension was filtered under reduced pressure through a bedof celite using a 5.5 cm Buchner funnel. The flask and filtercake wererinsed with 2×10 ml water.

A dark 1L one-neck, round-bottom flask equipped with a magnetic stirbar,addition funnel and nitrogen purge was charged with 375 ml acetic acid,and 10 ml 37% hydrochloric acid. The filtrate from the celite filtrationstep was charged to the addition funnel and added dropwise to thestirring acid solution over 30-45 minutes. Once the addition wascomplete, the pH was adjusted to about less than or equal to 1 by theaddition of hydrochloric acid. The suspension was stirred at 20-25° C.for 1-2 hours; then filtered under reduced pressure using a 7 cm Buchnerfunnel. The filtercake was rinsed with 2×10 ml water.

A dark 500 ml, one-neck, round-bottom flask equipped with a stirbar,condenser, and nitrogen purge was charged with tin mesoporphyrin wetcakefrom the above step and 200 ml 1N HCl. The suspension, which ideally hasa red color, was warmed to about 85-90° C. for 1-2 hours. The reactionwas cooled to 20-25° C. and the suspension was filtered under reducedpressure using a 7 cm Buchner funnel. The filter cake was rinsed with2×20 ml 0.1N HCl and dried at 85-90° C. for 24-48 hours. About 5 to 7 gof pharmaceutical grade pure tin mesoporphyrin chloride (tin (IV)mesoporphyrin IX dichloride) were obtained, for about a 50-70% yield,with a purity greater than or equal to 99%, as judged by HPLC analysis.

EXAMPLE 4 Representative Large Scale Production of Tin Mesoporphyrin IXChloride (Tin (IV) Mesoporphyrin IX Dichloride or Stannsoporfin)

Step 1

A 200 L reaction vessel, which has been pressure tested and inerted withnitrogen, is charged with 0.6 kg of 5% palladium on carbon (50% water byweight). Without agitation, the vessel is charged with 6.0 kg hemin and161.0 kg formic acid, while minimizing the exposure of the ingredientsthroughout this reaction to visible or ultraviolet light. The vessel ispressurized with hydrogen to 30-35 psi at 20-25° C. The reaction mixtureis agitated vigorously for a minimum of 30 minutes and warmed to 85-90°C. With vigorous agitation, the reaction temperature is maintained at85-90° C. with a hydrogen pressure of 45-55 psi for a period of 60-75minutes. The reaction is then cooled to 45-50° C. while maintainingpressure and hydrogenation is continued for a further 6 hours. Thereaction is cooled to 20-25° C. The reactor is depressurized and inerted(flushed) with nitrogen. The reactor is charged with a dispersion agent,such as 3.0 kg hyflo supercel, suspended in 36 kg formic acid. Thereaction mixture is then filtered to remove the catalyst.

The filtercake is rinsed with 2×61 kg formic acid. 170 L of the filtrateis transferred to a 200 L reaction vessel and cooled to 10-15° C. Thereaction mixture is distilled under a reduced pressure of 20-60 mmHg,with a maximum reactor temperature of 50° C., to a residual volume of25-35 L. The remainder of the filtrate is transferred into the reactorand cooled to 10-15° C. The reaction mixture is distilled under areduced pressure of 20-60 mmHg, with a maximum reactor temperature of50° C., to a residual volume of 25-35 L. The temperature of the reactoris cooled to 20-25° C. The reaction vessel is charged with 89.1 kgmethyl tert-butyl ether over a minimum of 1 hour. Upon completion of theaddition, the reaction is agitated at 20-25° C. for a minimum of 2hours. The reaction mixture is cooled to −20 to −25° C. over a minimumof 1 hour. The reaction is agitated at −20 to −25° C. for a period of 4hours. The suspension is filtered through a cotton terylene cloth at −20to −25° C. The filtercake is rinsed with 2×6 kg methyl tert-butyl ether.The product is dried under vacuum with a maximum oven temperature of 55°C. until it passes drying specifications. Once dry, the product(mesoporphyrin IX formate) is packaged. The theoretical yield for thisreaction is 6.1 kg. Typically, the product is isolated with a yield of4.6-5.8 kg (75-95%).

Step 2

An inerted reaction vessel is charged with 5.3 kg tin (II) chloride, 1.1kg ammonium acetate, and 45.3 kg acetic acid. The suspension ismoderately agitated at 20-25° C. for a minimum period of 2 hours. Aninerted 200 L reaction vessel is charged with 4.6 kg mesoporphyrin IXformate from step 1, and 45.0 kg acetic acid. The mesoporphyrinsuspension is warmed to 45-55° C. with moderate agitation for a periodof 2 hours. With moderate agitation, under nitrogen, the tin chloridesuspension is transferred into the mesoporphyrin suspension whilemaintaining a temperature of 45-55° C. in the vessel. The transfer linesare rinsed with 5.9 kg acetic acid. With vigorous agitation, nitrogenand air are bubbled into the reaction at such a rate so as to maintainan oxygen level less than 2% within the reactor. This aeration ismaintained throughout the reaction. With vigorous agitation, thereaction mixture is warmed to reflux (ca. 110° C.) for a minimum periodof 3 hours.

The reaction is cooled to 60-70° C. and 45.8 kg purified (de-ionized)water is added over a minimum of 30 minutes. With moderate agitation,the reaction temperature is cooled to 20-25° C. over a minimum of 1hour. The reaction mixture is agitated at 20-25° C. for a minimum of 1hour. The product is filtered through a cotton terylene cloth and thefiltercake rinsed with 2×9 kg purified water. The wet filtercake istransferred to a 200 L reaction vessel followed by 30.1 kg purifiedwater, 4.6 kg 31% hydrochloric acid. The transfer lines are rinsed with5 kg purified water. With moderate agitation, the suspension is warmedto 85-90° C. for a period of 1-3 hours. The reaction mixture is cooledto 20-25° C. and 31.0 kg acetone is added over a minimum period of 30minutes. The suspension is agitated at 20-25° C. for a minimum of 1hour. The product is filtered through a cotton terylene cloth and thefiltercake rinsed with 2×6 kg acetone. The product is dried under astream of nitrogen on the filter until it passes drying specifications.Once dry, the crude product (substantially pure (about or more than 95%)tin (IV) mesoporphyrin IX dichloride) is packaged. The theoretical yieldfor this reaction is 5.3 kg. Typically, the crude, substantially puretin mesoporphyrin product is isolated with a yield of 4.0-4.8 kg (75-90%yield).

Step 3

An inerted 200 L reactor is charged with 1.8 kg crude, substantiallypure tin mesoporphyrin, formed via Steps 1 and 2, and 31 kg WFI (waterfor injection) with moderate agitation at 20-25° C. The reactor ischarged with 2.4 kg 28% ammonium hydroxide. The resultant solution isagitated at 20-25° C. for 30 minutes, prior to testing pH to ensure thatit is greater than 9. If not, additional ammonium hydroxide is added insmall portions until this pH level is achieved. To the resultantsolution is charged 0.1 kg Darco KB activated carbon and 0.2 kg hyflosupercel suspended in 2.3 kg purified water. With moderate agitation,the suspension is agitated at 20-25° C. for a minimum of 30 minutes. Thesuspension is filtered through a sparkler filter to remove solids,leaving a filtrate. The filter cake is rinsed with 13 kg purified water.An inerted 200 L reactor is charged with 69.3 kg acetic acid and 3.1 kg31% hydrochloric acid. With moderate agitation, under nitrogen whilemaintaining a temperature of 20-25° C. the filtrate is added to theacetic acid HCl solution over a minimum of 45 minutes. The resultantsuspension is agitated for 15 minutes at 20-25° C. prior to testing thepH level to ensure that the final pH is about less than or equal to 1.If not, additional hydrochloric acid is added in small portions untilthis pH level is achieved. The suspension is then agitated at 20-25 Cfor a minimum of 1 hour. The product is filtered through a cottonterylene cloth and the filter cake is rinsed with 2×5 kg purified water.

With moderate agitation, at 20-25° C., an inerted 200 L reactor ischarged with 31 kg purified water and 2.4 kg 28% ammonium hydroxide. Thesolution is then recirculated through the filtercake in order tocompletely dissolve all wetcake. The resultant solution is agitated at20-25° C. for 30 minutes, prior to testing pH to ensure that it isgreater than 9. If not, additional ammonium hydroxide is added in smallportions until this level is achieved. To the resultant solution ischarged 0.1 kg Darco KB activated carbon and 0.2 kg hyflo supercelsuspended in 2.3 kg purified water. With moderate agitation, thesuspension is agitated at 20-25° C. for a minimum of 30 minutes. Thesuspension is filtered through a sparkler filter to remove solids,leaving a filtrate. The filter cake is rinsed with 13 kg purified water.An inerted 200 L reactor is charged with 69.3 kg acetic acid and 3.1 kg31% hydrochloric acid. With moderate agitation, under nitrogen whilemaintaining a temperature of 20-25° C. the filtrate is added to theacetic acid HCl solution over a minimum of 45 minutes. The resultantsuspension is agitated for 15 minutes at 20-25° C. prior to testing thepH level to ensure that the final pH is about less than or equal to 1.If not, additional hydrochloric acid is added in small portions untilthis pH level is achieved. The suspension is then agitated at 20-25° C.for a minimum of 1 hour. The product is filtered through a cottonterylene cloth and the filter cake is rinsed with 2×5 kg purified water.

With moderate agitation, at 20-25° C., an inerted 200 L reactor ischarged with 31 kg purified water and 2.4 kg 28% ammonium hydroxide. Thesolution is then recirculated through the filtercake in order tocompletely dissolve all wetcake. The resultant solution is agitated at20-25° C. for 30 minutes, prior to testing pH to ensure that it isgreater than 9. If not, additional ammonium hydroxide is added in smallportions until this level is achieved. To the resultant solution ischarged 0.1 kg Darco KB activated carbon and 0.2 kg hyflo supercelsuspended in 2.3 kg purified water. With moderate agitation, thesuspension is agitated at 20-25° C. for a minimum of 30 minutes. Thesuspension is filtered through a sparkler filter to remove solids,leaving a filtrate. The filter cake is rinsed with 13 kg purified water.An inerted 200 L reactor is charged with 69.3 kg acetic acid and 3.1 kg31% hydrochloric acid. With moderate agitation, under nitrogen whilemaintaining a temperature of 20-25° C. the filtrate is added to theacetic acid/HCl solution over a minimum of 45 minutes. The resultantsuspension is agitated for 15 minutes at 20-25° C. prior to testing thepH level to ensure that the final pH is about less than or equal to 1.If not, additional hydrochloric acid is added in small portions untilthis pH level is achieved. The suspension is then agitated at 20-25° C.for a minimum of 1 hour.

The resulting product is filtered through a cotton terylene cloth andthe filter cake is rinsed with 2×5 kg purified water and 2×4 kg acetone.The filter cake product is dried under vacuum with a maximum oventemperature of 100° C. until it passes drying specifications. Once dry,the pharmaceutical grade pure product (tin (IV) mesoporphyrin IXdichloride or stannsopoifin) is packaged and is of pharmaceutical gradequality, as verified by analytical HPLC technique. The theoretical yieldfor this reaction is 1.8 kg. Typically, the final product is isolatedwith a yield of 1.1-1.6 kg (60-90%) and is pharmaceutical grade pure (atleast about or exceeding 97%).

EXAMPLE 5 Representative Large Scale Production of Tin Mesoporphyrin IXChloride (Tin (IV) Mesoporphyrin IX Dichloride or Stannsoporfin)

Step 1

Without agitation, a 200 L reaction vessel which has been pressuretested and inerted with nitrogen is charged with 0.6 kg of 5% palladiumon carbon (50% water by weight), 6.0 kg hemin and 161.0 kg formic acid,while minimizing the exposure of the ingredients throughout thisreaction to visible or ultraviolet light. The vessel is pressurized withhydrogen to 30-35 psi at 20-25° C. The reaction mixture is agitatedvigorously for a minimum of 30 minutes and warmed to 85-90° C. Withvigorous agitation, the reaction temperature is maintained at 85-90° C.with a hydrogen pressure of 55-65 psi for a period of 60-90 minutes. Thereaction is then cooled to 45-50° C. while maintaining pressure andhydrogenation is continued for a further 24-48 hours. The reaction iscooled to 20-25° C. The reactor is depressurized and inerted (flushed)with nitrogen. The reactor is charged with a dispersion agent, such as3.0 kg hyflo supercel and 2.3 kg of DARCO KB, suspended in 36 kg formicacid. The reaction mixture is then filtered to remove the catalyst.

The filtercake is rinsed with 122 kg formic acid. 170 L of the filtrateis transferred to a 200 L reaction vessel and cooled to 10-15° C. Thereaction mixture is distilled under a reduced pressure of 20-60 mmHg,with a maximum batch temperature of 50° C., to a residual volume of25-35 L. The remainder of the filtrate is transferred into the reactorand cooled to 10-15° C. The reaction mixture is distilled under areduced pressure of 20-60 mmHg, with a maximum batch temperature of 50°C., to a residual volume of 25-35 L. The temperature of the reactor iscooled to 20-25° C. The reaction vessel is charged with 89.0 kg methyltert-butyl ether over a minimum of 1 hour. Upon completion of theaddition, the reaction is agitated at 20-25° C. for a minimum of 2hours. The reaction mixture is cooled to −20 to −25° C. over a minimumof 1 hour. The reaction is agitated at −20 to −25° C. for a period of 4hours. The suspension is filtered through a cotton terylene cloth at −20to −25° C. The filtercake is rinsed with 2×6 kg methyl tert-butyl ether.The product is dried under vacuum with a maximum oven temperature of 60°C. until it passes drying specifications. Once dry, the product(mesoporphyrin IX formate) is packaged.

Purification of the Mesoporphyrin IX Formate

Excess metal catalyst is removed from the intermediate by chargingformic acid with mesoporphyrin IX formate and a quantity of a metalscavenger such as Si-Thiol (approximately 2-10% of the yield ofintermediate, based on calculation) with moderate agitation undernitrogen for 16 to 20 hours at 70-80 ° C. The metal scavenger and excesscatalyst is then removed by reducing the temperature to 20-25° C., andthen charging a filtering aid such as celite (−5% /0.3 kg) andadditional formic acid (-32 kg) into the mixture. The mixture is thenfiltered and vacuum distilled. The concentrated filtrate is slowly addedto a mixture of purified water (52 kg) and 31% hydrochloric acid (9.3kg) (by calculation based on the quantity of dry intermediate). Gentleagitation and a temperature of 20-25° C. is maintained for a period of2-3 hours. The resultant mesoporphyrin IX dihydrochloride in suspensionis isolated by filtration and dried on the filter while passing a streamof nitrogen through the filter.

The procedure described immediately above may be repeated at least oneor two more times for a total of at least 1-3 purifications. Adequateresults have been obtained with one purification step.

Step 2

An inerted 200 liter reaction vessel is charged with approximately 2.8kg of mesoporphyrin IX dihydrochloride, 3.3 kg tin chloride and 73kilogram acetic acid. The suspension is moderately agitated at 20-25°C., for a minimum of 30 minutes. The suspension is vigorously agitatedfor a minimum of 30 minutes at a temperature of 20-25° C., whilebubbling in a mixture of 6% oxygen in nitrogen. With vigorous agitationunder nitrogen and maintaining a 6% oxygen in nitrogen purge, thereaction mixture is heated to reflux (ca 115° C.) and maintained for 24to 26 hours.

The 6% oxygen in nitrogen purge is shut off. The reaction is cooled to60-70° C. and approximately 28 kg of purified (de-ionized) water isadded over a minimum of 30 minutes. With moderate agitation, thereaction temperature is cooled to 20-25° C. over a minimum of 30minutes. The reaction mixture is agitated at 20-25° C. for a minimum of1 hour. The product is filtered through a cotton terylene cloth and thefiltercake rinsed with 11 kg purified water. The wet filtercake istransferred to a 200 L reaction vessel followed by 40 kg purified water,6.6 kg 31% hydrochloric acid. The transfer lines are rinsed with 10 kgpurified water. With moderate agitation, the suspension is warmed to85-95° C. for a period of 1-2 hours. The reaction mixture is cooled to20-25° C. The suspension is agitated at 20-25° C. for a minimum of 30minutes. The product is filtered through a cotton terylene cloth and thefiltercake rinsed with 11 kg purified water. The product is dried undera stream of nitrogen on the filter until it passes dryingspecifications. Once dry, the crude product (substantially pure (aboutor more than 95%) tin (IV) mesoporphyrin IX dichloride) is packaged.Typically, the crude, substantially pure tin mesoporphyrin dichlorideproduct is isolated with a yield of 2.2 kg and 97% purity.

Step 3

An inerted 100 L reactor without agitation is charged with approx. 2.2kg crude, substantially pure tin mesoporphyrin dichloride, formed viaSteps 1 and 2; 0.3 kg hyflo supercel, 0.1 Kg DARCO KB, and 19 kg WFI(water for injection). With moderate agitation at the reactor is chargedwith 1.5 kg 28% ammonium hydroxide. The resultant solution is agitatedat 20-25° C. for 1 to 2 hours, prior to testing pH to ensure that it isequal to or greater than 9. If not, additional ammonium hydroxide isadded in small portions until this pH level is achieved. With moderateagitation, the suspension is agitated at 20-25° C. for a minimum of 1-2hours. The suspension is filtered through a filter to remove solids,leaving a filtrate. The filter cake is rinsed with 7 kg WFI. An inerted200 L reactor is charged with 58 kg acetic acid and 2.4 kg 31%hydrochloric acid. With moderate agitation, under nitrogen whilemaintaining a temperature of 20-25° C. the filtrate is added to theacetic acid/HCl solution over a minimum of 45 minutes. The resultantsuspension is agitated for a minimum of 15 minutes at 20-25° C. prior totesting the pH level to ensure that the final pH is about less than orequal to 1. If not, additional hydrochloric acid is added in smallportions until this pH level is achieved. The suspension is thenagitated at 20-25 C for 1-2 hours. The product is filtered through acotton terylene cloth and the filter cake is rinsed with 10 kg WFI.

The procedure described immediately above may be repeated at least oneor two more times for a total of at least 1-3 purifications. Adequateresults have been obtained with one purification step.

Without agitation, the wet filter cake and 26 kg WFI are transferredinto a 200 L reactor. With moderate agitation, under nitrogen at 20-25°C., 15.5 kg of 31% HCl and 5 kg WFI are charged into the reactor. Themixture is heated to 85-90° C. and agitated for 16-18 hours. Whilemoderately agitating the vessel contents, the temperature of the mixtureis lowered to 20-25° C. and the agitation is continued for at least onehour. The reaction mixture is then filtered. The filter cake is rinsedwith a mixture of 19 kg WFI and 0.7 kg 31% HCl.

The filter cake product is dried by passing a stream of nitrogen throughthe filter and applying heat to the filter apparatus until it passesdrying specifications. Once dry, the product (tin (IV) mesoporphyrin IXdichloride or stannsoporfin) is packaged and is of pharmaceutical gradequality and purity, as verified by analytical HPLC technique. Typically,the final product is isolated with a yield of 1.2 kg with a purityexceeding 97%).

While foregoing is directed to the preferred embodiment of the presentinvention, other and further embodiments of the invention may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method of producing a metal mesoporphyrin halide comprising:isolating a mesoporphyrin formate; and converting the mesoporphyrinformate to a metal mesoporphyrin halide.
 2. The method of claim 1,wherein the mesoporphyrin formate is converted directly to a metalmesoporphyrin halide.
 3. The method of claim 1, wherein themesoporphyrin formate is first converted to mesoporphyrindihydrochloride and the mesoporphyrin dihydrochloride is converted tothe metal mesoporphyrin halide.
 4. The method of claim 3, wherein themesoporphyrin dihydrochloride is reacted with insert metals to form themetal mesoporphyrin halide.
 5. The method of claim 3, further comprisingpurifying the mesoporphyrin formate in the presence of a metalscavenger.
 6. The method of claim 5, wherein the metal scavengerincludes Si-thiol.
 7. The method of claim 4, further comprisingcatalytically hydrogenating hemin in the presence of an acid to form themesoporphyrin formate.
 8. The method of claim 7, wherein the step ofcatalytically hydrogenating the hemin occurs in two steps.
 9. The methodof claim 8, further comprising heating a mixture of hemin and ahydrogenation catalyst under pressure at a first temperature for a firstperiod of time and subjecting the mixture to a second temperature underpressure for a second period of time.
 10. The method of claim 9, whereinthe first temperature is higher than the second temperature.
 11. Themethod of claim 1, wherein metal mesoporphyrin halide is a tinmesoporphyrin halide.
 12. The process of claim 10, further comprising:a) subjecting a reaction mixture of hemin and a hydrogenation catalystin an acid to hydrogen pressure of about 30-65 psi and then raising thetemperature to about 85-95° C. and maintaining the temperature withinthat range for a period of about 1-3 hours; b) subjecting the reactionmixture to a further hydrogen pressure of about 30-65 psi at atemperature range of about 45-50° C. for a period of about 24-48 hours;and c) recovering the formate salt of mesoporphyrin IX from the reactionmixture by precipitation of the mixture with a solvent.
 13. The processof claim 7, wherein the acid is formic acid.
 14. The process of claim12, wherein the solvent is an ether.
 15. The process of claim 14,wherein the solvent is methyl tert-butyl ether.
 16. The process of claim15, wherein the hydrogenation catalyst is palladium on carbon.
 17. Themethod of claim 1, wherein the quantity of metal mesoporphyrin halideformed by the process exceeds 0.1 kg.
 18. The method of claim 1, furthercomprising purifying the metal mesoporphyrin halide, including: a)dissolving the metal mesoporphyrin halide in an aqueous basic solutionto obtain a dissolved metal mesoporphyrin halide; b) treating saiddissolved metal mesoporphyrin halide with charcoal to obtain a treatedmetal mesoporphyrin halide; c) adding said treated metal mesoporphyrinhalide to a first aqueous acid solution to obtain a precipitated metalmesoporphyrin halide; d) triturating said precipitated metalmesoporphyrin halide in a second aqueous acid solution at elevatedtemperature to obtain a substantially pure metal mesoporphyrin halide;and e) drying said substantially pure metal mesoporphyrin halide. 19.The process of claim 18, wherein the metal mesoporphyrin halide is tin(IV) mesoporphyrin IX chloride.
 20. A method of producing stannsoporfincomprising: isolating mesoporphyrin IX formate in substantially pure,solid form; and converting the mesoporphyrin IX formate tostannsoporfin.
 21. The method of claim 20, further comprising convertingthe mesoporphyrin IX formate to mesoporphyrin IX dihydrochloride andreacting the mesoporphyrin dihydrochloride with a tin insert metal toform stannsoporfin.
 22. The method of claim 21, further comprisingpurifying the mesoporphyrin formate with a metal scavenger.
 23. Themethod of claim 22, wherein the metal scavenger includes a silica boundmetal scavenger.
 24. The method of claim 23, further comprisingpurifying the stannsoporfin to provide pharmaceutical gradestannsoporfin.